Cotton fabrics applications

CeUulases have appeared in a few laundry detergents around the world. Since there are few, if any, ceUulase-based soils present on home laundry, any laundering benefit from ceUulase would be expected to come from action on cotton fabric. The nature and magnitude of such benefits is uncertain (see Enzya s, Ejdusthial Applications). 

In general, metal complexes formed from bidentate azo chromogens are little used as dyes but do find important applications as pigments (section 2.3.2). Rare exceptions exist, however, such as the nickel(II) complex of p-nitroaniline— BON acid (5.11). This has been used for bordeaux prints of high light fastness on cotton fabrics. Two possible modes of bidentate attachment to the nickel atom can be envisaged (Scheme 5.2). 

Silver nanoparticles synthesized by a cost-effective three-stage electrochemical technique have demonstrated great promise as antimicrobial agents. Nanosilver was less effective against E. coli, S. aureus, B. subtilis and P. phoeniceum compared to silver ions. However silver nanoparticles have prolonged bactericidal effect as a result of continuous release of Ag ions in sufficient concentration and thus nanoparticles can be more suitable in some bactericidal applications. The synthesized silver nanoparticles added to water paints or cotton fabrics have demonstrated a pronounced antibacterial/antifungal effect, despite the fact that they tend to agglomerate into clusters up to 200 nm. 

Another fine-related problem that has seen some research effort is that of smolder resistance of upholstery and bedding fabrics. Finishing techniques have been developed to make cotton smolder-resistant (152—156), but the use of synthetic barrier fabrics appears to provide a degree of protection. Work also has provided a means of producing cotton fabrics that have both smooth-dry and flame-retardant performance (150,151). In this case, the application of FR treatment should be performed first, and DP treatment should be modified to accommodate the presence of the FR polymer on the fabric. 

Another group of chlorinated hydrocarbons comprises those made from paraffin wax. Major applications are in extreme pressure lubricants and as extenders and plasticizers in surface coatings and in vinyl plastics. The chlorinated waxes were also widely applied in flameproofing cotton fabrics, which led to large consumption by the military. It is believed that current military requirements for flame-resistant fabrics will be met by vinyl sheeting of vinyl-coated textile products, so that the World War II demand for the halogenated waxes will not be repeated. 

Tyndall, R.M. Application of Cellulase Enzymes to Cotton Fabrics and Garments, AATCC Book of Papers, 259-273 (1991). 

Fabric-Based Grades. Grade Cis made from cotton fabric weighing over 140 g/m2 (4 oz/yd2). The maximum thread count in any ply is 28/cm (72/in.) in the fill direction, and the maximum total thread count in the warp and fill directions is 56/cm (140/in.). Heavier fabrics provide higher impact strength but rougher machined edges. Its use for electrical applications is not recommended. 

It should be mentioned that the impact of excited metallotetrapyrroles on biological systems is not limited to the above areas. It was found and patented [280] that some water-soluble phthalocyanine complexes exhibit bactericidal action on wet cotton fabric exposed to air and solar radiation. Zn(TPPS) is one of the best sensitizers in photokilling the unarmoured dinoflagellate Ptychodis-cus brevis. In the future further directions of photobiological applications of metallotetrapyrroles may emerge. 

To impart fire retardancy, cotton fabrics are commonly treated with borates for applications such as drapes, clothing, rugs, fire-smothering blankets, and Christmas tree decorations. Recommended formulations include borax/boric acid, Polybor, boric acid/APP, or boric acid/ammonium phosphate. It should be noted that these borate treatments will be removed during laundering hence the treatment has to be reapplied. Much effort has been expended in trying to bond borate to cellulose fiber permanently with only partial success (see Section 9.2.6.1). 

The interactions between cellulose and ammonia have attracted industrial attention. Applications to wood [321-325] by treating it with liquid ammonia and with gaseous ammonia under pressure [326] to cotton fabrics [320,325-327], and to sewing treads [327] have been described. 

Many durable flame retardants for cotton have been developed to convey open-flame resistance [344,346,360,361]. The vertical flame test for determining the U.S. children s sleep-wear flammability (16 CFR 1615 and 1616) is a rather severe test and cotton fabrics require a FR treatment to pass the test. The test method requires treatments that are durable to 50 hot water wash and dry cycles. Currently there are relatively few commercially available FR chemistries that are durable under these conditions required today. Some of the reasons include low commercial availability of the chemicals, costs, safety concerns, process control issues, and difficulty in application. 

However, too low a wet pickup can be eqnally problematic and also lead to uneven finish distribution if the liquid phase is discontinuous. The concept of a critical application value (CAV) is useful when discnssing optimal wet pickups. The CAV is defined as the minimum amonnt of dnrable press finish liquid that can be applied to a given cotton fabric withont prodncing a non-uniform distribution of crosslinks after drying and curing. Dye staining tests can be used to determine these distributions. For non-cellulosic fibres, other methods of finish distribution analysis can be used. 

A third approach to reducing pilling tendency is applicable to 100 % cotton fabrics. As described in Chapter 17 on enzymatic finishes the use of cellulase enzymes during wet processing can remove enough of the loose fibres in the yams so that pilling is greatly reduced. 

Enzyme suppliers determine the activity of their products by measuring the extent of the catalysed reaction under carefully controlled conditions. A standard test exists for amylases (AATCC Test Method 103) , but the evaluation of cellulases is more complex and can vary from supplier to supplier. One common method is to measure the degradation of carboxymethylcellulose solutions. Another is to determine the weight or strength loss of standard cotton fabrics under laboratory conditions where there is a correlation problem, because the mechanical conditions of the technical application are different to the laboratory ones. For example, the hydrolysis degree, HD, is determined by HD = (m - m)/m where and m are the weight of the test material before and after bio-fmishing. 

Because these fire-retardant salts are water-soluble and subject to leaching, several new methods have been developed which provide a water-resistant or permanent treatment for cotton fabrics and cellu-losic materials. Perkin developed a process involving successive treatment with sodium stannate and ammonium sulfate, which precipitates stannic oxide in the cellulose libers. Antimony oxide in combination with vinyl chloride or other chlorinated polymers has also been found effective. A more recent approach to this problem involves application of fire-retardant resin-forming or cross-linking compounds. " These include materials and methods based on the copolymerization of tetrakis(hydroxymethyl)phosphonium chloride and methylol — melamine, the reaction of bromoform and triallyl phosphate to form a cross-linked polymer, and the cross-linking reaction of tris(l-aziridinyl)phosphine oxide with cellulose, or its copolymerization with tetrakis(hydroxymethyl)phosphonium chloride and other materials. ... 

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